Camera calibration is a critical step in a large variety of image processing applications. Most products which involve one or more cameras and perform image processing or analysis require a camera calibration step during manufacturing. It is desirable to be able to calibrate the camera accurately, as quickly as possible, while also requiring as small an area on the manufacturing floor as possible.
In traditional camera calibration methods, the camera(s) views a calibration target from one or more different positions. Calibration targets are rigid objects that contain known visual patterns that are possible to locate with great accuracy in images. Some approaches require the camera to view a planar, or two dimensional (2D), calibration target from many (four or more) different positions and distances. The planar target is often created by printing a pattern on a high resolution printer and then mounting it to a flat surface. The target contains fiducial points, such as checkerboard intersections, for which the relative three dimensional (3D) locations are precisely known. Other methods use a non-flat or 3D calibration target, in which case a single view is sufficient. Positioning the camera once is preferable for manufacturing since it is faster and enables a simpler manufacturing floor layout and work flow. However, 3D calibration targets typically require great manufacturing accuracy to place the target fiducials at precise locations, resulting in a high cost. Detecting the target features can also be more difficult on a 3D target.